Preparation and use of nanosize pigment compositions

ABSTRACT

A mixture of an organic nanosize pigment comprising of from 50 to 99% by weight of the nanosize pigment and 1 to 50% by weight based of a low molecular weight naphthalene sulfonic acid formaldehyde polymer and its use as a particle growth and crystal phase director for the preparation of a direct pigmentary organic pigment or in pigment finishing.

FIELD OF INVENTION

The present invention relates to a novel method for the preparation oforganic nanosize pigments and their use for example as additives todirect and control the growth and/or crystal phase of pigment particles.Such compounds are particularly useful when present during the synthesisor finishing of an organic pigment.

BACKGROUND OF THE INVENTION

Organic pigment nanoparticle thin film devices via Lewis acid pigmentsolubilization and in situ pigment dispersions are described by Hsieh,B. R.; Melnyk, A. R., Xerox Corporation, Webster, N.Y., USA, In theJournal of Imaging Science and Technology 45(1), 37-42 [2001].

A number of patents describe processes for the preparation of nanosizepigments. For example, U.S. Pat. No. 5,679,138 describes a process forthe preparation of ink jet inks comprising pigments with a pigmentparticle size of less than 100 nanometers prepared by milling thecorresponding pigments in a high speed mill and its use for inkjetprinters. EP-1,195,413 describes the production of finely dividedorganic pigments by precipitation in a micro jet reactor, with theresulting pigment suspension being removed by a gas or vaporized liquid.An example is given which provided copper tetrachloro phthalocyaninehaving an average particle size of 26±11 nm.

U.S. Pat. No. 6,225,472 and U.S. Pat. No. 6,406,533 describe6,13-dihydroquinacridone derivatives that can direct and control thegrowth and/or crystal phase of pigment particles.

U.S. Pat. No. 6,264,733 describes new pigment particle growth and/orcrystal phase directors of formula (MO₃S)_(m)-Q-(CH₂—(X)—(Y)_(n))_(o)(I), wherein Q represents a pigment moiety, M represents a metal cation,quaternary N cation or H, X is a aromatic group or a cyclo-heteroaliphatic group with at least one 5 atom or 6 atom ring or a heteroaromatic group with at least one 6 atom ring and which is not aphthalimido group, Y is a sulfonic acid or carboxylic acid or saltthereof; m and n independent of each other represent an integer fromzero to 2.5; and o is an integer from 0.05 to 4.

Although such compounds can effectively direct the growth and crystalphase of pigment particles when present during the pigment synthesis,they have the disadvantage of being a pigment derivative and thereforeneed to be separately synthesized first and are subject to additionalregulatory clearances.

The state of the art literature does not describe the use of nanosizepigment particles to induce pigment crystal growth or as crystal phasedirectors during pigment synthesis or pigment finishing.

SUMMARY OF THE INVENTION

It has now surprisingly been found that organic pigments in a nanosizedparticle form that is stabilized by low molecular weight naphthalenesulfonic acid formaldehyde polymers can be used effectively as crystalgrowth and crystal phase directors when present during the pigmentsynthesis or a pigment finishing step. They are particularly effectivefor quinacridone and diketopyrrolo pyrrole pigments.

Such nanosize pigment particles can be prepared by routine synthesisprocedures and offer the pigment manufacturer an efficient means toprepare a pigment having the preferred color characteristic withoutrequiring an additional pigment finishing step.

Thus, the inventive process allows the manufacturer to produce highperformance, high chroma organic pigments in an economical andenvironmentally friendly manner and therefore, is of significantcommercial importance.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for the preparation of organicpigments in a nanosize pigment particle size by dissolving the organicpigment in an acid and precipitation from the acidic solution in thepresence of a low molecular weight naphthalene sulfonic acidformaldehyde polymer into a liquid, which is preferably water. Theresulting suspension is filtered and the presscake consists of thepolymer and the pigment in a nanosize pigment particle form. It can, forexample, be used “as is” in the acidic wet form, or can be reslurried inwater or an organic solvent to provide a dispersion containing nanosizedpigment particles.

Furthermore the present invention relates to the use of such nanosizedpigment/naphthalene sulfonic acid formaldehyde polymer mixtures ascrystal growth and crystal phase directors when present during thepigment synthesis or a pigment finishing step,

Suitable organic pigments include organic pigments selected from thegroup consisting of azo, azomethine, methine, anthraquinone,phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo,thiazinindigo, dioxazine, iminoisoindoline, iminoisoindolinone,quinacridone, flavanthrone, indanthrone, anthrapyrimidine andquinophthalone pigments, or a mixture or solid solution thereof;especially a dioxazine, diketopyrrolopyrrole, quinacridone,phthalocyanine, indanthrone or iminoisoindolinone pigment, or a mixtureor solid solution thereof.

Preferred organic pigments are the quinacridone, anthraquinone,phthalocyanine, perylene, dioxazine, iminoisoindolinone,iminoisoindoline, diketopyrrolopyrrole and indanthrone pigments.

Highly preferred are quinacridone pigments of formula

wherein A and D are independently of one another H, F, Cl, C₁-C₃alkyl orC₁-C₃alkoxy.

The instant process is especially useful for the preparation ofnanosized particles of quinacridone, 2,9-dichloroquinacridone,2,9-difluoroquinacridone, 4,11-dichloroquinacridone,2,9-dimethyl-quinacridone and 2,9-dimethoxyquinacridone.

Additionally, the process is also suitable for the preparation of solidsolutions in a nanosized particle form containing one or morequinacridone components. Thus, an aspect of this invention relates tothe process wherein a mixture containing two or more quinacridones offormula (I) are co-precipitated by the inventive process to yield aquinacridone solid solution product.

The process of this invention is particularly practical for thepreparation of solid solution pigments in a nanosized particle form,such as quinacridone/2,9-dichloroquinacridone,quinacridone/4,11-dichloroquinacridone,quinacridone/2,9-dimethylquinacridone, quinacridone/2,9-dimethoxyquinacridone, 2,9-dichloroquinacridone/2,9-dimethylquinacridone,2,9-dichloroquinacridone/2,9-dimethoxyquinacridone,2,9-dimethylquinacridone/2,9-dimethoxyquinacridone, quinacridonequinone/quinacridone, 6,13-dihydroquinacridone/quinacridone orquinacridone/diketopyrrolopyrrole solid solutions as described forexample in U.S. Pat. No. 4,810,304.

The low molecular weight naphthalene sulfonic acid polymer according tothis invention has a molecular weight below 10000 and is preferablyrepresented by formula

wherein n is a number from 0 to 12, preferably from 1 to 5.Correspondingly, the average molecular weight is about from 400 to 3000,preferably from 648 to 1532.

The naphthalene sulfonic acid is 1- or 2-naphthalene sulfonic acid orpreferably a mixture of the 1- and 2-naphthalene sulfonic acids. Mostpreferably, the inventive naphthalene sulfonic acid formaldehyde polymeris prepared from a mixture of 1-naphthalene sulfonic acid and2-naphthalene sulfonic acid in a molar ratio of about 4:1.

The above naphthalene sulfonic acid formaldehyde polymer is added to thepigment at a concentration of from 1 to 50% by weight, preferably from10 to 45% by weight, based on the final pigment/polymer mixture. It canbe prepared separately and then be added before or during theprecipitation process of the pigment. Preferably, the naphthalenesulfonic acid formaldehyde polymer is prepared after dissolving thepigment, thus in the presence of the pigment, in the acid media.

The nanosized pigments are prepared for example by a process in whichthe pigment Is dissolved preferably in a mineral acid such as sulfuricacid or phosphoric acid. Then naphthalene sulfonic acid and formaldehydeare added preferably in a 1:1 molar ratio, which react to generate theinventive naphthalene sulfonic acid formaldehyde polymer followed byprecipitation of the pigment/polymer mixture into a precipitationmedium.

The precipitation medium is preferably water. Organic solvents,preferably water-soluble organic solvents such as for example a C₁ to C₅alcohol like methanol, ethanol, ethylene glycol, ethylene glycolmono-C₁-C₃alkyl ether, n-propanol, isopropanol, n-butanol or tert-amylalcohol or a mixture of organic solvents can be present in theprecipitation media in such concentration that there is no negativeimpact on the generation of the inventive nanosize pigments.

Additionally, it can be advantageous to neutralize the acid partially orcompletely during or after the precipitation process. Neutralizingagents are for example ammonia or organic amines or preferably thealkali hydroxides like aqueous sodium or potassium hydroxides.

Furthermore it is possible to add additives such as surfactants,antifoaming agents, Inorganic fillers such as talc or mica, UV-absorber,light stabilizers like hindered amines, resins or waxes before, duringor after the inventive precipitation process. The amount of theadditives is 0 to 40% by weight, preferably 0.1 to 20% by weight basedon the amount of the pigment.

Typically, the pigment, naphthalene sulfonic acid and formaldehyde areused in a 1:1:1 molar ratio. However more of the naphthalene sulfonicacid or formaldehyde may be used to achieve the inventive nanosizepigment particles in mixture with the desired polymeric product.Preferably, the molar ratio of the pigment:naphthalene sulfonicacid:formaldehyde is 1:1-1.2:1-2.

Advantageously, the reactions conditions are conducted in such a waythat little sulfonation of the pigment is occurring. Therefore, thepigment is dissolved preferably at a temperature below 65° C.,preferably at from 30 to 60° C., most preferably from 35 to 45° C., andthe reaction is carried out preferably at a temperature below 100° C.,most preferably at from 50 to 90° C.

Depending on the temperature and other reaction conditions like timingof the addition of naphthalene sulfonic acid and/or formaldehyde intothe pigment/sulfuric acid mixture, some further sulfonation of thenaphthalene sulfonic acid may occur, in particular to the naphthalenedisulfonic acid. The presence of polymers containing such naphthalenedisulfonic acid moieties is not prohibitive, as long they do notnegatively impact the particle size and further properties of theinventive nanosize pigments.

In a preferred embodiment, the corresponding pigment is dissolved inconcentrated (95-98%) sulfuric acid at a concentration of about 5 to 30%by weight, most preferably about 10 to 25% by weight at a temperaturebelow about 50° C., preferably at about 35 to 45° C. The naphthalenesulfonic acid, preferably a mixture of 1-naphthalene sulfonic acid and2-naphthalene sulfonic acid in a molar ratio of 4:1, is added to thepigment solution at a temperature below about 50° C., preferably atabout 35 to 45° C. and is also dissolved. Finally, the formaldehyde isadded, preferably in the form of para-formaldehyde, at a temperaturebelow about 55° C., preferably at 35 to 50° C. The reaction mixture isheated to a temperature of from about 50 to 90° C. and stirred at thattemperature until the reaction is complete, preferably for about 30minutes to 6 hours, most preferably from about 30 to 90 minutes, anddrowned into water having a temperature below 40° C., preferably below25° C. or ice water. The slurry is stirred for about 5 minutes to 6hours, preferably from about 30 minutes to 3 hours, at a temperature offrom about 0 to 50° C., preferably of from 10 to 25° C. The inventivecompounds are then isolated by filtration or centrifugation and can beused as is in its acidic presscake form or are washed to pH 4-7 withwater. The resulting product cake can again be used as is or bereslurried in water or a solvent to provide nanosize pigment containingdispersions or it can be dried.

Generally, the present reaction conditions favor the generation of apure nanosize pigment with the presence of only traces of thecorresponding mono or di naphthalene sulfonic acid methyl pigmentderivative of the formula

wherein n is 1 or 2 and Q is the radical obtainable by deprotonation ofthe pigment, usually by deprotonation of an OH or NH group.

However, the presence of such a derivative in a concentration of 0.01 to10% by weight based on the inventive nanosize pigment can have anadditional advantageous effect.

Any equipment can be used in which the precipitation from the acidsolution provides the inventive nanosize pigments with their desiredproperties. For example it can be carried out in a micro reactor asdescribed in published EP-1,195,413 or in a high turbulence drowningequipment as described in U.S. Pat. No. 3,607,336 or simply by drowningthe sulfuric acid pigment/naphthalene sulfonic acid polymer solutioninto water or ice/water in a vessel.

The isolated samples can be analyzed by known methods, for example, byelementary analysis or mass spectrometry such as LCMS, GCMS or thematrix-assisted laser desorption ionization technique (MALDI) or by theHPLC method, all of which are well known to those of ordinary skill inthe art. The particle size of the inventive nanosize pigment particlescan be obtained by the electron micrograph.

Typically, the inventive nanosize pigments have an average particle sizeof from 1 to 100 nm, preferably from 1 to 50 nm and most preferably from3 to 30 nm, as determined by the electron micrograph from an acidicaqueous dispersion.

Surprisingly, it was found that the inventive nanosizepigment/formaldehyde naphthalene sulfonic acid polymer mixtures couldact as effective crystal growth and crystal phase directors when presentduring the pigment synthesis or a pigment finishing step.

Generally, the inventive nanosize pigment/naphthalene sulfonic acidformaldehyde polymer mixtures when used as particle growth and crystalphase directors are added at a concentration of up to about 25% byweight, preferably from 0.1 to 15% by weight, more preferably from 0.3to 10% by weight and most preferably from 0.5 to 8% by weight, based onthe pigment to be synthesized, before or during the final steps ofpigment synthesis. The addition of pigment/naphthalene sulfonic acidformaldehyde polymer mixtures as particle growth and/or crystal phasedirectors has generally a negligible effect on the yield of the pigmentto be synthesized.

The inventive nanosize pigment/naphthalene sulfonic acid formaldehydepolymer mixtures growth and/or crystal phase directors are suitable asadditives for the synthesis of pigments of several pigment classesincluding pigments of the anthraquinone, phthalocyanine, perinone,perylene, diketopyrrolopyrrole, thiazinindigo, thioindigo,iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone,dioxazine, indanthrone, anthrapyrimidine and quinophthalone pigmentclasses.

The inventive nanosize pigment/naphthalene sulfonic acid formaldehydepolymer mixtures are particularly suitable for the synthesis of directpigmentary grade diketo pyrrolopyrrole and quinacridones and/or itssolid solutions. Said compounds are highly suitable for the synthesis ofquinacridone pigments in their specific crystal modifications, such asthe alpha, beta or gamma quinacridone, 2,9-dichloroquinacridone,2,9-dimethyl-quinacridone, 4,11-dichloroquinacridone and solid solutionsthereof.

Without limiting this invention to any particular theory, it is believedthat the inventive nanosize pigment particles can act as seeds for thepigments to be synthesized and the low molecular weight naphthalenesulfonic acid formaldehyde polymer can adhere to the synthesized pigmentmolecule and by doing so can further direct the crystal growth andcrystal phase. The term “directing the crystal growth” refers tocontrolling the synthesis of pigment particles to have a suitablepigmentary size as well as directing the growth of the crystals togenerate particles of a specifically desired shape, such as platelet,needle, cubic, leaflet, prismatic and other geometric forms, in adesired crystal phase. The effect can be influenced by the chemicalstructure of the organic pigment, the selection of the reaction mediaand the concentration and chemical structure of the inventive particlegrowth director compounds. Hence, usually it is preferable to usenanosize seeds of the same pigment class and/or even same crystal phaseas the desired pigment, most preferred identical to the desired pigment.

During the isolation of the pigment, for example in the filtration step,the polymer compounds—when soluble in the reaction media—can be washedout and H desirable, be recollected from the filtrate or wash liquid.Typically, traces of these compounds are partially left on the pigmentsurface and can have additional benefits. Such benefits are, forexample, improved pigment properties such as rheological properties,dispersibility and wetting behavior, flocculation resistance andimproved heat stability.

In certain cases, it is advantageous to use the inventive compounds inmixture or in combination with other additives including known pigmentparticle growth inhibitors such as, for example, phthalimidomethyl-,imidazolmethyl- or pyrazolmethyl-quinacridone, pigment sulfonic acids orspecific polymers; or other optional ingredients such as wetting agents,surfactants, defoamers, antioxidants, UV absorbers, light stabilizers,plastisizers, or general texture improving agents and so forth. Any suchadditional additives may be used as long as said additives are stableunder the pigment synthesis conditions and have no negative impact onthe final pigment properties or the environment. Generally, suchadditives can be used in a concentration of about from 0.1 to 25% byweight, preferably from 0.2 to 15% by weight and most preferably from0.5 to 8% by weight, based on the pigment to be synthesized.

Suitable specific polymers are, for example, polyacrylic acid,polymethacrylic acid, polyurethane, polyvinylalcohol,polyvinylpyrrolidone or cellulose derivatives.

Suitable surfactants include anionic surfactants such as alkylbenzene-or alkylnaphthalene-sulphonates, alkylsulfosuccinates or cationicsurfactants including, for example, quaternary salts such as benzyltributyl ammonium chloride; or nonionic or amphoteric surfactants suchas polyoxyethylene surfactants and alkyl- or amidopropyl betaines,respectively.

Suitable texture improving agents are, for example, fatty acids such aslauric, stearic or behenic acid, and fatty amines such as laurylamineand stearylamine. In addition, fatty alcohols or ethoxylated fattyalcohols, polyols such as aliphatic 1,2-diols or epoxidized soybean oil,waxes, resin acids and resin acid salts may be used for this purpose.

Suitable UV stabilizers are, for example, the benzotriazole derivativesknown under the trade names Tinuvin® or Ciba Fast® H Liquid (an arylsulfonated benzotriazol), both being products of Ciba SpecialtyChemicals Corporation.

Due to the ability to act as an antiflocculant as well as an excellentparticle growth inhibitor and phase director, the inventive nanosizepigment/naphthalene sulfonic acid formaldehyde polymer mixtures cangenerally be used in the pigment finishing, pigment treatment, orpigment application such as an additive during the pigment dispersionstep in bead mills, extruder, calander and so forth, as well as duringpigment synthesis.

The inventive nanosize pigment/naphthalene sulfonic acid formaldehydepolymer mixtures are themselves strongly colored and can be used ascoloring agents for the coloring of inorganic or organic substrates suchas mineral oil, paints, inks, color filters, fibers, plastics, paper,cosmetics and textiles. Such applications are well-known per se, forexample for colour filters from PCT/EP03/08654.

The following examples further describe some preferred embodiments ofthe invention, but do not limit the scope of the invention. In theexamples, all parts are by weight unless otherwise indicated.

EXAMPLE 1

A one liter flask equipped with a stirrer, thermometer, condenser anddrying tube is charged with 200 ml concentrated (95-98%) sulfuric acid.31.2 g unsubstituted quinacridone (Cromophtal® Red 2020, Ciba SpecialtyChemicals Inc.) are added at a temperature below 45° C. and the mixtureis stirred for 10 minutes at 40-45° C. to dissolve the pigment.

39.7 g of a wet naphthalene sulfonic acid sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium salt(Shanghai Shen Li Chemical Factory) are added at a temperature below 45°C. and the mixture is stirred for 15 minutes at 4045° C. followed by therapid addition of 3.2 g para formaldehyde. The reaction mixture isstirred for one hour at 58-60° C. then poured into 2.5 l ice water. Theviolet precipitate is stirred for 1 hours at 5-20° C., then filtered.The violet press cake is washed with water to a pH of about 2.5 and keptas presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water yieldinga red colored liquid which is filtered through paper to remove 1aggregated material. The fife is red and appears like a dye solution.However, the electron micrograph shows the quinacridone in nanosizeparticle form with an average particle size of 10 to 25 nm.

A small sample of the violet presscake is further washed to a pH of 5and dried and analytically tested by Matrix Assisted LaserDesorption/ionization (MALDI). When measured in positive mode, it showsas main component quinacridone (m/z 314 peak, and only a trace ofnaphthalene sulfonic acid methyl quinacridone (m/z 535 peak) is found asshown in FIG. 1.

When measured in negative mode, again the quinacridone is visible (m/z312 peak) and the polymeric structure of the naphthalene sulfonicacid-formaldehyde polymer is clearly visible with the main molecularweight peaks at 428, 649, 870, 1091, 1312, 1534, 1755 and 1976. Thenegative mode MALDI spectrum is shown in FIG. 2.

EXAMPLE 2

A one-liter flask equipped with a stirrer, thermometer, condenser anddrying tubs is charged with 200 ml concentrated (95-98%) sulfuric acid.17 g 2,9-dimethylquinacridone pigment (Cromophtal® Pink PT, CibaSpecialty Chemicals Inc.) is added at a temperature below 45° C. and themixture is stirred for 10 minutes at 40-45° C. to completely dissolvethe pigment.

19.9 g of a wet naphthalene sulfonic add sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium salt(Shanghai Shen Li Chemical Factory) are added at a temperature below 45°C. and the mixture is stirred for 30 minutes at 40-45° C. followed bythe rapid addition of 1.6 g para formaldehyde. The reaction mixture isstirred for one hour at 58-60° C. then poured into 2.5 liter ice water.The bluish violet precipitate is stirred for 1 hour at 5-20° C., andthen filtered. The violet press cake is washed with water to a pH of2-2.5 and kept as presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water yieldinga magenta colored liquid which is filtered through paper to removelittle aggregated material. The filtrate is magenta and appears like adye solution. However, the electron micrograph show the 2,9-methylquinacridone in nanosize particle form with an average particle size offrom 10 to 30 nm.

EXAMPLE 3

A one-liter flask equipped with a stirrer, thermometer, condenser anddrying tube is charged with 150 m concentrated (95-98%) sulfuric acid.14 g 2,9-dimethoxyquinacridone are added at a temperature below 45° C.and the mixture is stirred for 10 minutes at 40-45° C. to completelydissolve the pigment.

15 g of a wet naphthalene sulfonic acid sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium salt(Shanghai Shen Li Chemical Factory) are added at a temperature below 45°C. and the mixture is stirred for 15 minutes at 40 to 45° C. followed bythe rapid addition of 1.2 g paraformaldehyde. The reaction mixture isstirred for one hour at 58-60° C. then poured into 2.5 liter ice water.The bluish violet precipitate is stirred for 1 hours at 5-20° C., thenfiltered. The bluish violet press cake is washed with water to a pH of2-2.5 and kept as presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water,yielding a bluish violet colored liquid which is filtered through paperto remove little aggregated material. The filtrate is bluish violet andappears like a dye solution. However, the electron micrograph shows the2,9-dimethoxyquinacridone in nanosize particle form with an averageparticle size of from 10 to 30 nm.

EXAMPLE 4

A one-liter flask equipped with a stirrer, thermometer, condenser anddrying tuba is charged with 250 ml concentrated (95-98%) sulfuric acid.19.5 g 2,9-dichloroquinacridone pigment (Cinquasia® Magenta RT-265-D,Ciba Specialty Chemicals Inc.) are added at a temperature of 50° C. andthe mixture is stirred for 20 minutes at 48-52° C. to dissolve thepigment.

19.9 g of a we naphthalene sulfonic add sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium salt(Shanghai Shen Li Chemical Factory) are added at a temperature below 50°C. and the mixture is stirred for 30 minutes at 45-50° C. followed bythe rapid addition of 1.6 g paraformaldehyde. The reaction mixture isstirred for one hour at 58-60° C. then poured into 2.5 liter ice water.The violet precipitate is stirred for 1 hour at 5-20° C., and thenfiltered. The violet press cake is washed with little water to a pH of1.5-2.5 and kept as presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water,yielding a violet colored liquid which is filtered through paper toremove little aggregated material. The filtrate is violet and appearslike a dye solution. However, the electron micrograph shows the2,9-dichloro-quinacridone in nanosize particle form with an averageparticle size of from 10 to 25 nm.

EXAMPLE 5

A one-liter flask equipped with a stirrer, thermometer, condenser anddrying tube is charged With 200 ml concentrated (9M98%) sulfuric acid.21.4 g C.I. Pigment Red 254 (Irgazin® DPP Red BO, CIBA SpecialtyChemicals Inc.) is added and the mixture is stirred for 1 hour at 55-58°C.

23.9 g of a wet naphthalene sulfonic acid sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium sat(Shanghai Shen Li Chemical Factory) am added at a temperature below 70°C. and the mixture is stirred for 10 minutes at 70° C. followed by therapid addition of 1.9 g paraformaldehyde. The reaction mixture isstirred for one hour at 70-75° C., then poured into 2.7 liter ice water.The violet brownish precipitate is stirred for 1 hour at 5-20° C., thenfiltered. The press cake is washed with water to a pH of 2.0-3.0 andkept as presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water yieldinga violet colored liquid which is filtered through paper to remove littleaggregated material. The filter is brown and appears like a dyesolution. However, the electron micrograph shows the diketopyrrolopyrrole pigment in nanosize particle form with an average particle sizeof 10 to 30 nm.

EXAMPLE 6

A one-liter flask equipped with a stirrer, thermometer, condenser anddrying tube is charged with 200 ml concentrated (95-98%) sulfuric acid.15 g C.I. Pigment Blue 60 (Cibanon® Blue RS PT 9860, Ciba SpecialtyChemicals Inc.) arm added at a temperature below 45° C. and the mixtureis stirred for 15 minutes at 40-45° C. to completely dissolve thepigment.

10.7 g of a wet naphthalene sulfonic acid sodium salt presscake with asolid content of 58%, a mixture containing 80% 1-naphthalene sulfonicacid sodium salt and 20% 2-naphthalene sulfonic acid sodium salt(Shanghai Shen Li Chemical Factory) are added at a temperature below 50°C. and the mixture is stirred for 10 minutes at 40-45° C. followed bythe rapid addition of 1.6 g paraformaldehyde. The reaction mixture isstirred for one hour at 60-65° C. then poured into 2.5 liter ice water.The dark bluish precipitate is stirred for 1 hour at 5-20° C., and thenfiltered. The dark bluish press cake is washed with water to a pH of1.5-3.0 and kept as presscake.

About 0.5 g of the press cake are reslurried in 20 ml hot water yieldinga blue colored liquid which is filtered through paper to remove littleaggregated material. The filtrate is blue and appears like a dyesolution. However, the electron micrograph shows the indanthrone pigmentin nanosize particle form with an average particle size of from 10 to 30nm.

EXAMPLE 7

A one liter flask equipped with a thermometer, stirrer and condenser ischarged with 50 g 6,13-dihydroquinacridone, 200 ml methanol, 1 gpolyvinylpyrrolidone powder (Luviskol® K-30, BASF) and 7 g of theaqueous presscake of the nanosize quinacridone/naphthalene sulfonic acidformaldehyde polymer mixture according to Example 1 are stirred at20-27° C. for 10 minutes. 50 g 50% aqueous sodium hydroxide are added.The mixture is stirred under a slow flow of nitrogen at 50-53° C. forone hour. 0.8 g anthraquinone mono sulfonic acid sodium salt as catalystis added and the reaction mixture is heated to reflux for 10 minutes. 76g of an aqueous 18.9% by weight hydrogen peroxide solution are addedinto the reaction mixture with a peristaltic pump at a pumping rate of0.4 ml/minute, whereby after 25 minutes addition time 1.6 gphthalimidomethyl-quinacridone are introduced into the reaction mixturefollowed by continuing the hydrogen peroxide addition while maintainingreflux and a slow nitrogen flow. The resulting violet suspension isfurther stirred for 10 minutes at reflux then diluted with 100 ml coldwater and filtered. The presscake is washed with hot water then dried,yielding a violet quinacridone.

The product shows a high purity and less then 0.1% remaining6,13-dihydro-quinacridone as determined by a spectrophotometer method.The X-ray diffraction pattern of the pigment shows the characteristicsof a beta quinacridone. When incorporated into automotive paints, theproduct leads to a strong violet color dispersion with excellentrheological properties and an attractive color appearance when drawn ona contrast carton, which dispersion can easily be sprayed on metallicpanels generating coatings of excellent durability (a topcoat may thenfurther be applied in conventional manner, for example by the wet-on-wettechnique).

EXAMPLE 8

A one liter flask equipped with a thermometer, stirrer and condenser ischarged with 50 g 6,13-dihydroquinacridone, 200 ml methanol, 1 gpolyvinylpyrrolidone powder (Luviskol® K-30, BASF) and 7 g of theaqueous presscake of the nanosize quinacridone/naphthalene sulfonic acidformaldehyde polymer mixture according to Example 1, are stirred at20-27° C. for 10 minutes. 73 g 50% aqueous sodium hydroxide are added.The mixture is stirred under a slow flow of nitrogen at 50-53° C. for 30minutes. 4.6 g of a 37% aqueous solution of anthraquinone-2,7-disulfonicacid disodium salt as catalyst is added followed by 10 ml water and thereaction mixture is heated to reflux for 40 minutes. 79 g of an aqueous18.2% by weight hydrogen peroxide solution are added into the reactionmixture with a peristaltic pump at a pumping rate of 0.4 ml/minute,whereby after 20 minutes addition time 2.3 g phthalimidomethyl-quinacridone and after another 70 minutes 0.3 gphthalimidomethyl-quinacridone are introduced into the reaction mixturefollowed by continuing the hydrogen peroxide addition while maintainingreflux and a slow nitrogen flow. The resulting violet suspension isfurther stirred for 10 minutes at reflux then diluted with 100 ml coldwater and filtered. The presscake is washed with hot water then dried,yielding a violet quinacridone.

The product shows a high purity and less then 0.1% remaining6,13-dihydro-quinacridone as determined spectrophotometrically. TheX-ray diffraction pattern of the pigment shows the characteristics of abeta quinacridone. When incorporated in automotive paints or plastics,the product leads to a strong violet color with excellent properties.

EXAMPLE 9

The procedure of Example 8 is repeated, but using 4 g of the aqueouspresscake of the nanosize 2,9-dimethylquinacridone/naphthalene sulfonicacid formaldehyde polymer mixture according to Example 2 instead of 7 gof the aqueous presscake of the nanosize quinacridone/naphthalenesulfonic acid formaldehyde polymer mixture presscake according toExample 1. A violet beta quinacridone pigment of similar good pigmentproperties is obtained.

EXAMPLE 10

The procedure of Example 8 is repeated, but using 4 g of the aqueouspresscake of the nanosize 2,9-dimethoxy quinacridone/naphthalenesulfonic acid formaldehyde polymer mixture according to Example 3instead of 7 g of the aqueous presscake of the nanosizequinacridone/naphthalene sulfonic acid formaldehyde polymer mixturepresscake according to Example 1. A violet beta quinacridone pigment ofsimilar good pigment properties is obtained.

EXAMPLE 11

The procedure of Example 8 is repeated, but using 4 g of the aqueouspresscake of the nanosize 2,9-dichloro quinacridone/naphthalene sulfonicacid formaldehyde polymer mixture according to Example 4 instead of 7 gof the aqueous presscake of the nanosize quinacridone/naphthalenesulfonic acid formaldehyde polymer mixture presscake according toExample 1. A violet beta quinacridone pigment of similar good pigmentproperties is obtained.

EXAMPLE 12

A one liter flask equipped with a thermometer, stirrer and condenser ischarged with 50 g 6,13-dihydroquinacridone, 200 ml methanol and 5 g ofthe aqueous presscake of the nanosize quinacridone/naphthalene sulfonicacid formaldehyde polymer mixture according to Example 1 are stirred at20-27° C. for 10 minutes. 50 g 50% aqueous sodium hydroxide are added.The mixture is stirred under a slow flow of nitrogen at 50-53° C. forone hour. 0.9 g anthraquinone-2,7-disulfonic acid disodium salt ascatalyst is added and the reaction mixture is heated to reflux for 5minutes. 77 g of an aqueous 19.1% by weight hydrogen peroxide solutionare added into the reaction mixture with a peristaltic pump at a pumpingrate of 0.4 ml/minute, whereby after 15 minutes addition time 1.6 gphthalimidomethyl-quinacridone are introduced into the reaction mixturefollowed by continuing the hydrogen peroxide addition while maintainingreflux and a slow nitrogen flow. The resulting red suspension is furtherstirred for 10 minutes at reflux then diluted with 100 ml cold water andfiltered. The presscake is washed with hot water then dried, yielding ared quinacridone. The X-ray shows the diffraction pattern of a gammaquinacridone. The pigment shows outstanding pigment properties and canbe applied for the red coloration of paints, inks and plastics.

EXAMPLE 13

63.0 g of polyvinyl chloride, 3.0 g epoxidized soy bean oil, 2.0 g ofbarium/cadmium heat stabilizer, 32.0 g dioctyl phthalate and 1.0 g ofthe violet beta quinacridone pigment according to Example 7 are mixedtogether in a glass beaker using a stirring rod. The mixture is formedinto a soft PVC sheet with a thickness of about 0.4 mm by rolling for 8minutes on a two roll laboratory mill at a temperature of 160° C., aroller speed of 25 rpm and friction of 1:1.2, by constant folding,removal and feeding. The resulting soft PVC sheet is colored in anattractive violet shade and has excellent fastness to heat, light andmigration.

EXAMPLE 14

5 g of the violet beta quinacridone pigment according to Example 8, 2.65g Chimassorb® 944LD (hindered amine light stabilizer), 1.0 g Tinuvin®328 (benzotriazole UV absorber) and 2.0 g Irganox® B-215 Blend(anti-oxidant, all from Ciba Specialty Chemicals Corporation), are mixedtogether with 1000 g of high density polyethylene at a speed of 175-200rpm for 30 seconds after flux. The fluxed, pigmented resin is chopped upwhile warm and malleable, and then fed through a granulator. Theresulting granules are molded on an injection molder with a 5 minutedwell time and a 30 second cycle time at a temperature of 200, 250 and300° C. Homogeneously colored chips, which show a violet color withpractically no color differences, are obtained. They have an excellentlight stability.

EXAMPLE 15

This Example illustrates the incorporation of the inventive betaquinacridone according to Example 8 into an automotive paint system.

Millbase Formulation

A pint jar is charged with 30.9 g acrylic resin, 16.4 g AB dispersantconsisting of 45% of an acrylic resin in toluene, and 42.8 g solvent(Solvesso® 100, American Chemical). 30.0 g beta quinacridone accordingto Example 8 and 980 g of 4 mm diameter steel diagonal rods are added.The mixture in the jar is shaken on a Skandex shaker for 5 hours. Themillbase contains 25.0% pigment with a pigment/binder ratio of 0.5.

Masstone Color

48.9 g of the above millbase, 71.7 g of a clear 47.8% solids unpigmentedresin solvent solution containing a melamine resin catalyst, anon-aqueous dispersion resin and a UV absorber, and 29.4 g of a clearunpigmented 58% solids unpigmented polyester urethane resin solventsolution, are mixed and diluted with a solvent mixture comprising 76parts xylene, 21 parts butanol and 3 parts methanol to a spray viscosityof 20-22 seconds as measured by a #2 Fisher Cup.

The resin/pigment dispersion is sprayed onto a panel twice at 1½ minuteintervals as basecoat. After 2 minutes, the clearcoat resin is sprayedtwice at 1½ minute intervals onto the basecoat. The sprayed panel isthen flashed with air in a flash cabinet for 10 minutes and then “baked”in an oven at 129° C. for 30 minutes, yielding a violet colored panel.The coated panel has excellent weatherability.

EXAMPLE 16

1000 g of polypropylene granules (Daplen PT-55®, Chemie Linz) and 10 gof the gamma quinacridone pigment according to Example 12 are thoroughlymixed in a mixing drum. The granules so obtained are melt spun at260-285° C. to red filaments of good light fastness and textile fiberproperties.

EXAMPLE 17

1000 g of polypropylene granules (Daplen PT-55®, Chemie Linz) and 10 gof the beta quinacridone pigment according to Example 9 are thoroughlymixed in a mixing drum. The granules so obtained are melt spun at260-285° C. to violet filaments of good light fastness and textile fiberproperties.

1. A composition comprising from 50 to 99% by weight of an organicpigment having an average particle size of from 1 to 100 nm and from 1to 50% by weight of a naphthalene sulfonic acid formaldehyde polymerhaving an average molecular weight of from 400 to
 10000. 2. Acomposition according to claim 1, wherein the naphthalene sulfonic acidformaldehyde polymer has an average molecular weight of 400 to
 3000. 3.A composition of claim 1, wherein the pigment is selected from the groupconsisting of azo, azomethine, methine, anthraquinone, phthalocyanine,perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazinindigo,dioxazine, iminoisoindoline, iminoisoindolinone, quinacridone,flavanthrone, indanthrone, anthrapyrimidine and quinophthalone pigments,and mixtures and solid solutions thereof.
 4. A composition of claim 3,wherein the pigment is selected from the group consisting ofquinacridone, anthraquinone, phthalocyanine, perylene, dioxazine, iminoisoindolinone, imino isoindoline, diketopyrrolopyrrole and indanthronepigments and a mixture and solid solution thereof.
 5. A composition ofclaim 4, wherein the pigment is a quinacridone of formula

wherein A and D are independently of one another H, F, Cl, C₁-C₃alkyl orC₁-C₃alkoxy.
 6. A composition of claim 4, wherein the pigment is abinary or ternary solid solution of quinacridone and/ordiketopyrrolopyrrole pigments.
 7. A composition according to claim 1,wherein the polymer has formula

wherein n is a number from 0 to
 12. 8. A composition according to claim7, wherein the naphthalene sulfonic acid formaldehyde polymer comprises,as part of its backbone, 1-naphthalene sulfonic acid and/or2-naphthalene sulfonic acid moieties.
 9. A composition according toclaim 8, wherein the 1-naphthalene sulfonic acid and 2-naphthalenesulfonic acid moieties are in a 4:1 molar ratio. 10-21. (canceled)
 22. Acomposition according to claim 1, wherein the organic pigment has anaverage particle size of from 1 to 50 nm.
 23. A composition according toclaim 1, wherein the organic pigment has an average particle size offrom 3 to 30 nm.
 24. A composition according to claim 1, wherein thenaphthalene sulfonic acid formaldehyde polymer has an average molecularweight of 648 to
 1532. 25. A composition according to claim 22, whereinthe naphthalene sulfonic acid formaldehyde polymer has an averagemolecular weight of 400 to
 3000. 26. A composition according to claim22, wherein the naphthalene sulfonic acid formaldehyde polymer has anaverage molecular weight of 648 to
 1532. 27. A composition of claim 22,wherein the pigment is selected from the group consisting of azo,azomethine, methine, anthraquinone, phthalocyanine, perinone, perylene,diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine,iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone,indanthrone, anthrapyrimidine and quinophthalone pigments, and mixturesand solid solutions thereof.
 28. A composition of claim 23, wherein thepigment is selected from the group consisting of azo, azomethine,methine, anthraquinone, phthalocyanine, perinone, perylene,diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine,iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone,indanthrone, anthrapyrimidine and quinophthalone pigments, and mixturesand solid solutions thereof.
 29. A composition of claim 24, wherein thepigment is selected from the group consisting of azo, azomethine,methine, anthraquinone, phthalocyanine, perinone, perylene,diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine,iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone,indanthrone, anthrapyrimidine and quinophthalone pigments, and mixturesand solid solutions thereof.
 30. A composition of claim 25, wherein thepigment is selected from the group consisting of azo, azomethine,methine, anthraquinone, phthalocyanine, perinone, perylene,diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine,iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone,indanthrone, anthrapyrimidine and quinophthalone pigments, and mixturesand solid solutions thereof.
 31. A composition according to claim 2,wherein the organic pigment has an average particle size of from 3 to 30nm.
 32. A composition of claim 2, wherein the pigment is selected fromthe group consisting of azo, azomethine, methine, anthraquinone,phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo,thiazinindigo, dioxazine, iminoisoindoline, iminoisoindolinone,quinacridone, flavanthrone, indanthrone, anthrapyrimidine andquinophthalone pigments, and mixtures and solid solutions thereof.